1. Field of the Invention
This invention pertains to sensors of the type which change resistivity or current in a circuit in response to the presence of an adsorbate medium gas or liquid.
2. Description of the Prior Art
U.S. Pat. No. 3,045,198 describes an adsorption type detection device which employs electrically conductive adsorbent particles resiliently attached to a surface with an electrical conductive path being formed through the particles. These particles will, due to adsorption forces in absorbates of greater than about 9.0 Van der Waals Constant, become separated in the presence of an adsorbate medium to change the resistivity through the electrical conductive path in the sensor. The adsorbent particles used and described in U.S. Pat. No. 3,045,198 are of substantially uniform size such as 0.001 inch mean diameter. This uniform size was considered to be a requirement for an effective sensor.
U.S. pending patent application Ser. No. 841,802, filed Oct. 13, 1977 discloses another type sensor also using adsorbent particles. In this sensor a voltage is applied to the sensor to a level at which the current no longer increases linearly. When exposed to an adsorbate of Van der Waals Constant values below or above about 9.0 the current through the sensor or voltage across the sensor changes to a new level in the non linear region.